The Saudi Tadawul All-Shares Index, the largest in the Arab world, dipped 3.3 percent to 8,113.22 points, a 12-month low.

Leading the decline was the petrochemicals sector, with Saudi Basic Industries Co. SABIC losing 5.6 percent.

The main index on the Qatar Exchange, the second biggest bourse in the Gulf, dived 7.2 percent to 10,959.0 points, a level last seen in early January. Market leaders in banking and industry contributed to the slide.

US benchmark West Texas Intermediate for January delivery plunged to $58.80 per barrel — the lowest level since May 20, 2009 — having already closed under the psychological level of $60 on Thursday.

Brent crude for January meanwhile slipped to $62.75 in morning London deals, striking a low point last witnessed on July 16, 2009.

The oil market — which has shed almost 50 percent since June — plumbed the latest lows after the Paris-based IEA slashed its 2015 demand outlook, despite plunging prices.

The six nations of the Gulf Cooperation Council — Bahrain, Kuwait, Oman, Qatar, Saudi Arabia and United Arab Emirates — depend heavily on oil revenues which make up around 90 percent of their total income. (AFP)